1. Technical Field
The present invention relates to a liquid crystal display, and more particularly, to a liquid crystal display having touch sensing functionality and touch sensing method thereof.
2. Description of the Prior Art
Liquid crystal displays (LCDs) have advantages of a thin profile, low power consumption, and low radiation, and are broadly adopted for application in media players, mobile phones, personal digital assistants (PDAs), computer displays, and flat screen televisions. Utilization of LCDs to perform touch input functions has steadily become the mainstream, making application of touch-sensitive LCDs increasingly widespread. Touch-sensitive LCDs employ touch panels, which includes resistive touch panels and capacitive touch panels. Resistive touch panels locate touch input positions through voltage drops, but are unable to provide multitouch input functionality. Capacitive touch panels typically include sensing capacitors, and perform signal processing on capacitance variations of the sensing capacitors corresponding to touch points to locate touch input positions.
FIG. 1 is a structural diagram schematically showing a prior-art touch panel device. As shown in FIG. 1, the touch panel device 100 includes a touch panel 101, a plurality of readout lines 110, a plurality of sensing capacitors 120, a plurality of storage capacitors 140, and a plurality of comparators 150. When the touch panel 101 is touched, capacitance of a sensing capacitor 120 corresponding to a touch point changes, causing capacitor voltage thereof to change. The change in capacitor voltage is transmitted to the corresponding storage capacitor 140 through the corresponding readout line 110, and the corresponding comparator 150 compares the capacitor voltage of the storage capacitor 140 with a reference voltage Vref to generate a touch readout signal Sro.
However, as dimensions of the touch panel 101 increase, trace resistance of the readout lines 110 increases, such that the change in capacitor voltage of the sensing capacitor 120 transmitted to the storage capacitor 140 experiences a voltage drop due to the trace resistance, causing reduced touch sensitivity. Further, as parasitic capacitance of the readout lines 110 increases with increased size of the touch panel 101, transmission delay of the capacitor voltage from the sensing capacitor 120 to the storage capacitor 140 also increases, lowering responsiveness of the touch panel 101. Finally, the touch panel 101 that is externally attached to a display cannot meet the requirements of thin profile, low cost displays having touch sensing functionality.